JP3515563B2 - Injection molding method of multilayer hollow body made of synthetic resin - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is obtained by primary molding in which a pair of semi-hollow bodies are injection-molded using a fixed mold and a slide mold so as to have an abutting portion, and the primary molding. The inner layer molding for molding a single-layer hollow body from the secondary molding for molding the hollow body from the pair of semi-hollow bodies by joining the abutting portions of the pair of semi-hollow bodies, and the outer surface of the single-layer hollow body The present invention relates to an injection molding method for a synthetic resin multi-layer hollow body, which comprises outer layer molding in which an outer layer is injection-molded or is formed by repeating outer layer molding.

[0002]

2. Description of the Related Art Hollow tanks made of synthetic resin are widely used in various fields for liquids, gases, and powders. Such tanks, for example, fuel tanks, oil tanks, steering oil tanks, brake oil tanks of automobiles, are formed from sheet metal by various processes such as bending, drawing, welding, and rust prevention coating. Along with the reduction in weight, lighter synthetic resin tanks have been proposed.

The applicant of the present invention has disclosed such a synthetic resin tank in Japanese Patent Application Laid-Open Nos. 2000-43100 and 2000-1678.
It can be molded by a number of injection molding methods proposed by No. 85 and the like. A fixed mold and a slide mold are used for carrying out this molding method. This fixed mold has a core protruding outward from the parting line and a concave recessed inward, and the slide mold has a concave part that cooperates with the core of the fixed mold and a fixed mold. A core cooperating with the mold recess is provided. Therefore, when the slide mold is clamped with respect to the fixed mold at a predetermined position, the first cavity is formed by the core of the fixed mold and the recess of the slide mold, and the recess of the fixed mold and the core of the slide mold are formed. And form a second cavity. When the molten resin is injected into these first and second cavities in the primary molding, a pair of semi-hollow bodies are molded. With the primary molded product remaining in the slide mold, slide it to the second position, and then clamp the mold.
Then, the pair of semi-hollow bodies are abutted at the joint. The molten resin is injected into the joint by the secondary molding. Then, a hollow body in which a pair of semi-hollow bodies is integrated is obtained.

According to the above-mentioned injection molding method proposed by the present applicant, it is possible to manufacture or mold a completely sealed hollow body and also to manufacture a hollow body having a uniform wall thickness, and it is complicated. It has the advantage that it can handle various shapes. Further, when molded from ABS resin, AS resin, polyamide or the like, a hollow body having impact resistance can be obtained, and when molded from polypropylene or the like, a hollow body having chemical resistance can be obtained. However, if the impact resistance is emphasized, the chemical resistance becomes inferior, whereas if the chemical resistance is emphasized, the hollow body is weak against impact. Further, the conventional hollow body having a single layer is not always perfect in terms of evaporation of the contents. Therefore, a hollow body composed of two layers in which the outer layer and the inner layer have respective functions is also desired. Such a two-layer synthetic resin tank can be molded by blow molding. The head of the blow molding machine for two-layer molding includes a main nozzle that pushes out the main material layer, a first sub nozzle that pushes out the adhesive layer, a second sub nozzle that pushes out the inner layer, and the like.
Therefore, by extruding the respective resin materials from these nozzles, a semi-molded article composed of two layers in which the outer layer and the inner layer are adhered is obtained. By appropriately finishing this semi-molded product, a synthetic resin tank having an inner layer can be obtained.

[0005]

As described above, the blow molding can also be used to mold a synthetic resin tank, that is, a hollow body made of an inner layer and an outer layer. However, by blow molding, it is difficult to obtain a hollow body having a uniform thickness, and it is difficult to deal with a hollow body having a complicated shape. Further, since the head has the multi-layer structure as described above, there is a drawback that the blow molding apparatus is expensive and therefore the hollow body made of synthetic resin obtained by blow molding is expensive. In addition, a special process is required to finish the product into a hollow body, which increases the cost. Furthermore, there is a possibility that traces of finishing may remain and the appearance shape may be damaged. Therefore, an object of the present invention is to provide an injection molding method for a synthetic resin multi-layer hollow body, which is capable of inexpensively molding a multi-layer hollow body having a uniform thickness and a complicated shape.

[0006]

In the present invention, an injection molding method is applied to achieve the above object. According to the injection molding method, since the shape is formed by the mold, the wall thickness is uniform and the appearance shape is not damaged. An outer layer is formed on the outer surface of the hollow body formed by such an injection molding method by injection molding similarly using a mold. That is, in order to achieve the above object, the invention according to claim 1 is a primary molding in which a fixed mold and a slide mold are used to perform injection molding of a pair of semi-hollow bodies so as to have a butt portion. An inner layer molding for molding a single-layer hollow body from a secondary molding for molding a hollow body from a pair of semi-hollow bodies by joining abutting portions of a pair of semi-hollow bodies obtained by the primary molding; A single-layer hollow body is inserted into a recess formed by a fixed mold and a movable mold, and molten resin is injected into the cavity formed by the outer surface of the inserted single-layer hollow body and the inner surface of the recess. Two layers of hollow bodies are injection-molded from outer layer molding in which the outer layer is molded by injection. The invention according to claim 2 is a primary molding in which a pair of semi-hollow bodies are injection-molded using a fixed mold and a slide mold so as to have a butt portion, and a pair obtained by the primary molding. The inner layer molding for molding a single-layer hollow body from the secondary molding for molding the hollow body from a pair of semi-hollow bodies by joining the abutting parts of the semi-hollow body, and the fixed mold for the single-layer hollow body. An outer layer molding in which a molten resin is injected into a cavity formed by the outer surface of the inserted single-layer hollow body and the inner surface of the recess, and the outer layer is formed by inserting the hollow resin into a recess formed by the movable mold and Injection-molding a two-layer hollow body from
The outer layer is formed by inserting the molten resin into a cavity that is formed by the outer surface of the inserted two-layer hollow body and the inner surface of the recess, which is inserted into a recess formed by another fixed mold and a movable mold. Three layers of hollow bodies are injection-molded from the outer layer molding to be molded, and thereafter outer layer molding is repeated to mold the hollow body of the desired layer.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION First, an embodiment of a mold used for carrying out the primary molding and secondary molding of the present invention will be described, and then a molding example of a hollow body having an inner layer or a single layer will be described. Next, the mold used for the outer layer molding and the outer layer molding method will be described. FIG. 1A is a cross-sectional view showing the slide mold 20 with the mold closed at the first position. As shown in FIG. 1, the mold according to the present embodiment is A fixed mold 1 located on the right side in (a) of FIG. 1, a mold opening / closing operation with respect to this fixed mold 1, and a slidable drive in the vertical direction in (a) of FIG. The slide mold 20 is roughly configured. A fixed platen to which the fixed mold 1 is fixedly mounted, a movable platen that drives the slide mold 20 in the mold opening / closing direction, and a slide mold 20 that slides vertically in FIG. The drive device, the ejector device provided on the slide mold 20, the mold clamping device, etc. are shown in FIG.
Not shown in.

In the substantially central portion of the fixed mold 1, (a) of FIG.
As shown in FIG. 1, a first sprue 2 for primary molding is provided so as to cross the fixed mold 1. The first sprue 2 for primary molding extends in the vertical direction by the runner 3, and the second and third sprues 4 for primary molding,
5 in series. The second sprue 4 is provided on the top of the stationary core of the stationary mold 1 described later, and the third sprue 5 is provided.
Respectively open to the fixed side concave portions. A sprue 6 for secondary molding is provided below the sprue 2 for primary molding at a predetermined interval from the sprue 2 for primary molding. The sprue 6 for secondary molding is open to the parting line P side and communicates with the concave groove 7 formed on the parting line P side of the slide mold 20. The groove 7 reaches the side surface of the slide-side annular core 27 of the slide mold 20 described later.

At a position above the first sprue 2 for primary molding of the fixed mold 1, a fixed-side core 11 of a predetermined size having a square side surface protruding outward from the parting line P is formed. Are formed. A small fixed side annular core 12 is formed around the fixed side core 11 at a predetermined distance from the fixed side core 11. Fixed core 1
Reference numeral 1 denotes a slide side concave portion 21 of a slide mold 20 described later.
And the second cavity Cb for molding the second semi-hollow body, which is smaller than the slide-side recess 21 by the thickness of the semi-hollow body.

A fixed-side concave portion 15 having a predetermined depth is formed at a lower position of the fixed mold 1 so that a side surface of the fixed mold P has a substantially square shape. The fixed-side concave portion 15 is composed of a bottom wall 17 and a peripheral wall 18 rising from the periphery of the bottom wall 17. The bottom wall 17 of the fixed-side recess 15 has a small recess 1 with a relatively small diameter and a predetermined depth.
6 is formed. The support portion is integrally formed in the first semi-hollow body by the small recessed portion 16. The bottom wall 17 of the fixed-side recess 15 has a third sprue 5 for primary molding opened therein. The fixed-side recessed portion 15 formed in this way forms a first cavity Ca for molding a first semi-hollow body in cooperation with a slide-side core 25 of a slide mold 20 described later.

Above the slide mold 20, a slide-side recess 21 having a substantially square side surface is formed, which opens to the parting line P side. This slide side recess 2
The reference numeral 1 includes a bottom wall 22 and a peripheral wall 23 standing upright from the periphery of the bottom wall 22. On the bottom wall 22 of the slide-side recess 21, a small recess 2 having a relatively small diameter and a predetermined depth is provided.
6 is formed. The support portion is integrally formed in the second semi-hollow body by the small recess 26. The slide-side concave portion 21 thus configured is larger than the fixed-side core 11 of the fixed mold 1 described above by the thickness of the second semi-hollow body. As a result, the second cavity Cb for molding the second semi-hollow body having a predetermined wall thickness is formed. Further, the slide-side recess 21 and the fixed-side annular core 12 of the fixed mold 1 mold half of the joint space in the second semi-hollow body during the primary molding.

At a predetermined position below the slide mold 20,
A slide-side core 25 is formed so as to protrude outward from the parting line P. This slide side core 25 is
The first cavity Ca is formed in cooperation with the fixed-side concave portion 15 of the fixed mold 1 to mold the first semi-hollow body, and the thickness of the first semi-hollow body is larger than that of the fixed-side concave portion 15. The thickness is small. Further, a slide-side annular core 27 is formed around the base of the slide-side core 25 so as to surround the slide-side core 25 at a predetermined distance from the slide-side core 25. This slide side annular core 27
Allows the first mold to cooperate with the fixed-side concave portion 15 of the fixed mold 1,
Half of the joint space is molded into the semi-hollow body.

Next, the fixed mold 1 and the slide mold 2 described above.
A molding method will be described in which a pair of semi-hollow bodies are molded by primary molding using 0 and 0, and then a pair of semi-hollow bodies are joined by secondary molding to form a single-layer hollow body.

The slide mold 20 is clamped to the fixed mold 1 at the first position shown in FIG. Then, the fixed-side core 11 of the fixed mold 1 and the slide-side concave portion 21 of the slide mold 20 constitute a second cavity Cb for molding the second semi-hollow body. Further, the fixed-side concave portion 15 of the fixed mold 1 and the slide-side core 25 of the slide mold 20 constitute a first cavity Ca for molding the first semi-hollow body.

First sprue 2 for primary molding of fixed mold 1
A molten resin for primary molding is injected in the same manner as conventionally known. The molten resin passes from the first sprue 2 through the runner 3 and the second and third sprues 4 and 5 for primary molding to the second,
One cavity Cb, Ca is injection filled.
By this primary molding, a pair of first and second semi-hollow bodies A, B
Are simultaneously molded. At this time, as shown in FIG. 1B, the cross section of the second semi-hollow body B has a substantially trapezoidal cross section due to the fixed gold side annular core 12 and the slide side recess 21. The half-joint space Sb forming half of the joint space S and the joint space S having a substantially trapezoidal cross section due to the slide-side annular core 27 and the fixed-side recess 15.
The half-joint space portion Sa that composes one half is molded. In addition, the first and second semi-hollow bodies A and B are integrally formed with supporting portions Ha and Hb protruding outward at their side portions.

After waiting for a certain degree of cooling and solidification, the slide mold 20 is opened by a predetermined interval. Then slide mold 2
0 in the opening of the first semi-hollow body A with the second semi-hollow body B attached to the slide mold 20.
Slide to a second position where the openings of the are aligned. Then, the mold is clamped. Then, the first and second semi-hollow bodies A,
The opening of B is in contact, and the annular joining space S is closed by the half joining spaces Sa and Sb. In this way, the state where the mold is clamped and the joint space S is formed is shown in FIG.
It is shown in (b).

Molten resin for secondary molding is injected from an injection machine. The molten resin is injected and filled from the secondary molding sprue 6 of the fixed mold 1 through the concave groove 7 into the joining space S. As a result, the first and second semi-hollow bodies A and B are integrated, and a single-layer hollow body Tab made of synthetic resin is obtained. After waiting for cooling and solidification, the slide mold 20 is opened. The single-layer hollow body Tab is projected by the ejector pin. Hereinafter, the above operation is repeated to form a single-layer hollow body Tab.

Next, an embodiment of a mold used for molding the outer layer will be described. As shown in FIG. 2A, the outer layer molding die includes a fixed die 30 and a movable die 40 that is opened and closed with respect to the fixed die. The fixed mold 30 is provided with a recess 31 that is open to the parting line P side. The recess 31 is composed of a bottom wall 32 and a peripheral wall 33, and is larger than the single-layer hollow body Tab by a predetermined amount. The bottom wall 32 has a single-layer hollow body Ta.
A small concave portion 34 into which the support portion Ha of b is inserted is formed. The fixed mold 30 is provided with the first sprue 35. The first sprue 35 branches into second and third sprues 37 and 38 via a runner 36. The second and third sprues 37 and 38 open near the peripheral wall 33 that forms the recess 31 of the fixed mold 30. Therefore, the molten resin injected from the second and third sprues 37 and 38 is filled along the peripheral wall 33.

As shown in FIG. 2A, the movable mold 40 is also provided with a recess 41 which is open to the parting line P side. The recess 41 is composed of a bottom wall 42 and a peripheral wall 43, and is larger than the single-layer hollow body Tab by a predetermined amount. The bottom wall 42 has a single-layer hollow body Ta.
A small recess 44 into which the support portion Hb of b is inserted is formed.

Next, an example of molding the outer layer using the molds 30 and 40 will be described. The movable mold 40 is opened, and the single-layer hollow body Tab described above is inserted by a robot or the like so that the supporting portion Ha thereof enters the small recess 34 of the fixed mold 30. At this time, although not shown in the figure, positioning is performed by an auxiliary tool or the like. Then, the mold clamping of the movable mold 40 is started. The other supporting portion H of the single-layer hollow body Tab
When the position of the tip of b into the small recess 44 of the slide mold 40 is determined, the auxiliary tool is taken out and the mold is clamped. Then, the outer surface of the single-layer hollow body Tab and the recess 31 of the solid mold 30 and the recess 41 of the movable mold 40 constitute a cavity Cs for molding the outer layer. The state in which the single-layer hollow body Tab is inserted and the mold is clamped is shown in FIG.

Molten resin for the outer layer is injected from the first sprue 35. The molten resin is injected and filled into the cavity Cs from the second and third sprues 37 and 38, as shown and shown in FIG. At this time, since the second and third sprues 37 and 38 are opened along the peripheral wall 33 of the recess 31, the effect on the single-layer hollow body Tab is small.
As a result, the outer layer Ss is partially fused around the hollow body Tab without deforming the single-layer hollow body Tab. After cooling and solidification, the movable mold 40 is opened to obtain a hollow body T2 having two layers. Same as below 2
A hollow body T2 consisting of layers is formed.

The present invention is not limited to the above embodiment and can be implemented in various forms. For example, in the above-described embodiment, the pair of first and second semi-hollow bodies A and B are joined by the injection molten resin at the time of the secondary molding.
As described in Japanese Patent Application Laid-Open No. 7-16945, a heater can be used for secondary molding to fuse the bonded portion. Further, the hollow body T2 having two layers obtained as described above is inserted into another mold to form a hollow body having three layers, and by repeating this, four layers, five layers, etc. are formed. It is also clear that hollow bodies consisting of multiple layers can be molded. Further, in the above-described embodiment, the thickness of the outer layer Ss is uniform, but the thickness of the outer layer Ss depends on the size of the recess 31 of the fixed mold 30 and the recess 41 of the movable mold 40 depending on the purpose. Clearly, it can be adjusted.

Further, in the above embodiment, the fixed mold 30 and the movable mold 40 are arranged laterally, and the single-layer hollow body Tab is used.
Since the supporting portions Ha and Hb of the above are formed on the side portions, the positioning can be inserted into the small recesses 34 and 44 when inserting, so that the fixed mold 30 and the movable mold 40 are arranged in the lateral direction. In both vertical arrangements, insert positioning can be easily performed. Further, by changing the positions of the small recesses 34 and 44 and the support portions Ha and Hb, the thickness of the outer layer Ss can be freely controlled. Furthermore, the positions of the second and third sprues 37 and 38,
It is also clear that the shape, the number, etc. are not limited to the illustrated embodiment. It is also possible to apply or spray an adhesive to the surface of the hollow body before inserting it into the mold to obtain a multi-layer hollow body having a high bonding strength.

[0024]

As described above, according to the present invention, the primary molding in which a pair of semi-hollow bodies are injection-molded so as to have an abutting portion using a fixed mold and a slide mold, and the primary molding Inner layer molding for molding a single-layer hollow body from secondary molding for joining abutting parts of a pair of semi-hollow bodies obtained by molding to form a hollow body from a pair of semi-hollow bodies, and hollowing of the single layer The body is inserted into a recess formed by a fixed mold and a movable mold, and a molten resin is injected into a cavity formed by the outer surface of the inserted single-layer hollow body and the inner surface of the recess to form the outer layer. Since a two-layer hollow body is molded from the outer layer molding to be molded,
Alternatively, the outer layer molding is repeated to form a desired layer of the hollow body, that is, the molding is performed by injection molding using a mold, so that even a multi-layer hollow body having a uniform wall thickness and a complicated shape can be molded at low cost. To be

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of a mold used for primary and secondary molding of the present invention, in which (a) shows the mold with the slide mold closed at a first position. Sectional view, part (b)
FIG. 4 is a cross-sectional view showing only a main part in a state where secondary molding is performed.

FIG. 2 is a diagram showing an embodiment of a die for molding an outer layer and an embodiment of the present invention, in which (a) is a sectional view showing an embodiment of the die with a single-layer hollow body inserted. (B) is a cross-sectional view schematically showing a state in which the outer layer is being formed.

[Explanation of symbols]

1 Fixed Mold 11 Fixed Side Core 15 Fixed Side Recess 20 Sliding Mold 21 Sliding Side Recess 25 Sliding Side Core 30 Fixed Mold 31 Recess 40 Movable Mold 41 Recess A First Semi-Hollow Body B Second Semi-Hollow Body Tab Single layer hollow body Ss Outer layer T2 Three layer hollow body

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (2)

(57) [Claims] 1. A primary molding in which a pair of semi-hollow bodies are injection-molded using a fixed mold and a slide mold so as to have an abutting portion, and a pair of semi-hollow bodies obtained by the primary molding. The inner layer molding for molding a single-layer hollow body from the secondary molding for joining the abutting portions of to form a hollow body from a pair of semi-hollow bodies, and the single-layer hollow body for a fixed mold and a movable mold. And an outer layer molding in which a molten resin is injected into a cavity formed by the outer surface of the inserted single-layer hollow body and the inner surface of the recess to form an outer layer. A method for injection molding a synthetic resin multi-layer hollow body for injection molding a hollow body. 2. Primary molding in which a pair of semi-hollow bodies are injection-molded using a fixed mold and a slide mold so as to have a butt portion, and a pair of semi-hollow bodies obtained by the primary molding. The inner layer molding for molding a single-layer hollow body from the secondary molding for joining the abutting portions of to form a hollow body from a pair of semi-hollow bodies, and the single-layer hollow body for a fixed mold and a movable mold. And an outer layer molding in which a molten resin is injected into a cavity formed by the outer surface of the inserted single-layer hollow body and the inner surface of the recess to form an outer layer. A hollow body is injection-molded, the two-layer hollow body is inserted into a concave portion formed by another fixed mold and a movable mold, and the outer surface of the inserted two-layer hollow body and the inner surface of the concave portion. The outer layer is formed by injecting molten resin into the cavity composed of Three layers of the hollow body by injection molding, injection molding process a synthetic resin multilayer hollow bodies for molding a hollow body of a desired layer by repeating the outer layer forming less and a.